1. Field of the Invention
The present invention relates to a printed circuit board apparatus and, in particular, to a printed circuit board and a method and apparatus for mounting heavy or high heat generating components thereon.
2. Description of the Related Art
Generally, printed patterns such as a copper leads are formed on one side of a printed circuit board; components having leads are mounted on the other side. The leads pass through holes on the circuit board and are soldered to lands of the printed patterns.
In mounting heavy parts or high heat components on the circuit board, eyelets are first mounted into holes of the circuit board. This is done to prevent the possible breakage of the circuit board due to separation of the copper leaf from the board caused either by the weight of the components or by the heat deterioration of the circuit board.
FIG. 1 is a perspective view of a printed circuit board apparatus of the prior art. A heavy component or part 20 with leads 22 is mounted on one side (i.e. a part mounting side) 24 of a circuit board 26. Printed patterns 28 are formed on the other side (i.e. printed pattern side) 30 of circuit board 26. Eyelets 32 are fixed to board 26 by positioning them through holes 34 formed on board 26. The ends portion of leads 22, from part mounting side 24, are inserted through holes (cylindrical portions) in eyelets 32 and are soldered to lands 36 of printed patterns 28.
FIGS. 2 (A) through (D) are perspective, sectional and plan views of eyelet 32 shown in FIG. 1. The manner of fixing eyelet 32 to the circuit board is described below with reference to FIG. 2. Eyelet 32, shown in FIG. 2(A), is inserted through hole 34 of printed circuit board 26 from part mounting side 24 (FIG. 2(B)); the end of eyelet 32 projects from printed pattern side 30. One end of eyelet 32 is then curled by a saw-tooth punch, for example, the present punch shown in FIG. 10. By utilizing this curling process, eyelet 32 is fixed to the circuit board, as shown in FIG. 2(C). Curling portion 38 is formed in a continuous ring-shaped or annular configuration on printed pattern side 30, as shown in FIG. 2(D).
FIGS. 3 and 4 are perspective views of curling portion 38 after utilizing the prior art curling method. As shown in these Figures, portion 38 has a generally annular and convex configuration. FIG. 3 shows eyelet 32 with four interrupted sections 381 of curling portion 38 caused by breakage during the curling process. FIG. 4 shows eyelet 32 having a substantially continuous ring-shaped portion 38.
FIG. 5 shows a sectional view of a printed circuit board using an eyelet mounted by the present method. After the curling of eyelet 32, and lead 22 of component 20 is inserted in the hole of eyelet 32, solder 40 is then applied from printed pattern side 30. Soldering is implemented by using, for example, an automatic flow soldering machine. Due to the high viscosity of solder, it is difficult for solder to enter into curling portion 38 whether eyelet 32 has interrupted sections 381 (see FIG. 3) or substantially continuous section (see FIG. 4). As a result, a cavity 42 will form in many cases. The presence of cavity 42 will contribute to breaking of the soldered joint if either a load is added to lead 22 or repeated thermal expansion occurs.
For example, in TVs using printed circuit boards, it is desirable to decrease the length of lead cords, and preferably position them on the circuit board to facilitate assembly and reduce cost. In the event that heavy or high heat generating components are mounted on the boards, breaking of the soldered joints can occur.